Mineral In A Matrix (Likely Quartz Or Feldspar)

Quartz Druze on Matrix

Silicon Dioxide (SiO2)

Possible shale or slate fragment

Fine-grained clay-rich rock; possibly slate (low-grade metamorphosed shale)

Weathered granite-like rock

Granite, likely biotite-bearing; exact identification is uncertain from the image

Iron-stained garnet-bearing rock, possibly almandine garnet

Garnet-group silicate, likely almandine (Fe₃Al₂Si₃O₁₂), in a quartz–iron-oxide matrix

Possible dark igneous rock

Indeterminate; likely basalt or fine-grained mafic rock

Schorl (Black Tourmaline) in Quartz/Feldspar Matrix

NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH)

Weathered schist or foliated metamorphic rock

Mica schist, possibly phyllite; exact identification requires a fresh surface and testing

Quartz (Milky/Smoky variety on matrix)

Silicon Dioxide (SiO2)

Dalmatian Stone

Peralkaline Quartz-Feldspar Rock with Arfvedsonite

Weathered granite or granitic gneiss

Granite: quartz, feldspar, and mica; possibly gneiss if the dark minerals are banded

Granite (likely weathered biotite granite)

Coarse-grained felsic plutonic rock; quartz + alkali feldspar/plagioclase + biotite/hornblende

Quartz-rich metamorphic fragment (likely mica schist)

Mica schist, probably muscovite–quartz schist

Polished black septarian nodule (likely septarian agate)

Septarian concretion composed mainly of microcrystalline quartz/chalcedony, dark calcite or aragonite, and brown iron-oxide mineralization

Gneiss with Quartz Veining

Gneiss (High-grade Metamorphic Rock)

Sandstone

Arenite (primarily Quartz and Feldspar composition)

Tumbled gray feldspar-rich stone, possibly granite or quartzite

Indeterminate; likely quartz–feldspar aggregate, potentially fine-grained granite or quartzite

Pink Granite with Quartz Vein

Phaneritic Plutonic Felsic Rock (K-feldspar + Quartz + Plagioclase + Mica)

Rhyolite (Porphyritic / Vesicular)

Rhyolite

Potassium Feldspar (Orthoclase)

KAlSi3O8 (Potassium Aluminum Silicate)

Weathered schist or gneiss fragment

Quartz–feldspar–mica metamorphic rock; likely mica schist or gneiss

Red Granite

Felsic Intrusive Igneous Rock

Likely weathered igneous rock fragments

Indeterminate; possibly basaltic or granitic rock with quartz, feldspar, and dark mafic minerals

Spherulitic Rhyolite / Leopard Skin Rhyolite

Extrusive felsic igneous rock with spherulites

Weathered granite or granitic pegmatite

Coarse-grained quartz–feldspar–mica rock; likely granite, possibly pegmatitic granite

Sandstone

Sandstone (SiO2 dominant, with minor feldspar and clay minerals)

Sandstone

Arenite (Siliclastic sedimentary rock)

Banded Sedimentary Rock (Siltstone/Mudstone with concretion)

Siltstone with Ferruginous Banding

Unakitized Granite

Granite / Altered Monzonite with Epidote

Quartzite with Feldspar and Mica (Granitic Gneiss Pebble)

Metamorphic Rock / Quartzite / Granitic Gneiss

Quartz Vein on Matrix

Silicon Dioxide (SiO2)

Graywacke (Sandstone)

Graywacke Sandstone

Quartz-rich pegmatitic rock (likely quartz–feldspar–mica specimen)

Granitic pegmatite; mainly quartz (SiO₂), feldspar, and dark mica/amphibole

Granite pebble

Granite, typically quartz–feldspar–mica aggregate

Iron-stained quartz or quartz-rich rock

Quartz (SiO₂), likely milky quartz with hematite/goethite staining

Weathered granite cobble

Granite, typically quartz–alkali feldspar–plagioclase with biotite or hornblende

Rough Quartz Crystal in Matrix

Silicon Dioxide (SiO2)

Likely foliated metamorphic rock (quartz-mica schist or gneiss)

Quartz–feldspar–mica metamorphic rock; exact identification requires a fresh surface and tests

Mixed rounded fieldstones, likely granite and gneiss

Granite (quartz–feldspar–mica) and gneiss; exact identification is uncertain from the photograph

Rounded weathered rock, likely basalt or andesite

Fine-grained mafic to intermediate volcanic rock; precise identification requires testing

Gneiss (Metamorphosed Pebble)

Gneiss with Quartz/Feldspar banding

Granitic Pegmatite Intrusion in Host Rock

Pegmatite dike in amphibolite or schist

Granitic Pegmatite with Schorl

Granitic Pegmatite (NaAlSi3O8, KAlSi3O8, SiO2) with Schorl (NaFe3Al6(BO3)3Si6O18(OH)4)